Medical images are achieved as follows. Energy such as radiant ray containing X-rays, gamma rays, magnetic waves, ultrasonic waves or the like for measurement is irradiated to a subject (subject being examined), transmission signals or reflection signals of the subject being examined which are achieved by the energy irradiation are subjected to data processing, and the inside of the subject being examined is imaged on the basis of the data processing result.
From the viewpoint of protecting subjects being examined, it has been recently required to reduce the energy to be irradiated to a subject being examined for the purpose of measurement of exposure of X-ray or the like in the measurement of the medical images. On the other hand, high-quality images are required even under irradiation of reduced energy.
Both the requirements are incompatible with each other. As one method of satisfying these requirements is known a technique of removing a noise signal component which is increased due to suppression of the energy for the measurement, thereby enhancing the S/N ratio.
A conventional image processing method is disclosed in [Patent Document 1]. [Patent Document 1] has a step of emphasizing the sharpness of each pixel of first image data to achieve sharpened image data, a step of smoothening each pixel of the first image data to achieve smoothened image data, a step of calculating the edge degree of each pixel of the first image data, a step of setting the correlation between the edge degree and a fusion rate so that the fusion rate of the smoothened image data is increased with respect to the mode value of the calculated edge degree, and an image data fusing step of fusing the sharpened image data and the smoothened image data every pixel on the basis of the correlation between the edge degree and the fusion rate to achieve second image data. According to this method, both the edge enhancement and the particular noise reduction can be effectively compatible with each other.
Patent Document 1: JP-A-2003-132352